This document relates to wireless communications.
Wireless communication systems can include a network of one or more base stations to communicate with one or more wireless devices such as a mobile device, cell phone, wireless air card, mobile station (MS), user equipment (UE), access terminal (AT), or subscriber station (SS). Each base station can emit radio signals that carry data such as voice data and other data content to wireless devices. A base stations can be referred to as an access point (AP) or access network (AN) or can be included as part of an access network. Further, a wireless communication system can include one or more access networks to control one or more base stations. A wireless device can use one or more different wireless technologies for communications. Various wireless technologies examples include Long-Term Evolution (LTE), Code division Multiple Access (CDMA) such as CDMA2000 1x, High Rate Packet Data (HRPD), Universal Mobile Telecommunications System (UMTS), High Speed Packet Access (HSPA), and Worldwide Interoperability for Microwave Access (WiMAX).
Various wireless communication system can use Orthogonal Frequency Division Multiplexing (OFDM) technology to transmit and receive wireless signals. In some implementations, wireless communication system can use Orthogonal Frequency Division Multiple Access (OFDMA), which is a multi-user version of OFDM technology. The multiple access is achieved in OFDMA by assigning subsets of orthogonal subcarriers to individual subscriber stations. OFDMA may be viewed as a combination of frequency domain and time domain multiple access where radio resources are partitioned in a time-frequency space, and network user data bursts are assigned along the OFDM symbol index as well as OFDM sub-carrier index. OFDMA has been widely adopted by various standard bodies.
Wireless communication systems can use a media access control (MAC) layer to communicate data between a wireless device and a base station. A wireless communication system can use a MAC protocol data unit (PDU) to encapsulate data for transmission. A MAC PDU (MPDU) can include a header, can include data payload, and can include error detection information. A MPDU can include one or more full or partial service data unit (SDUs). A SDU can include one or more bytes of data associated with a connection.